While there's no magic number for R&D spending, the Pentagon is spending less than experts recommend.

Many revolutionary technologies have sprung from Defense Department laboratories over the years, but the Pentagon’s current funding levels for research and development are well below what they should be, researchers found.

In fiscal 2017, the Pentagon allocated $13.4 billion for “science and technology,” a broad category that encompasses basic and applied research, and developments of advanced technology, according to the Congressional Research Service.

That sum amounts to roughly 2.3 percent of the department’s overall budget, and while there’s no magic number for R&D spending, the 2001 Quadrennial Defense Review recommended the Pentagon devote 3 percent of its funds to science and technology.

Though a shortfall of less than one percent difference may seem insignificant, it equates to spending roughly $4 billion below what experts recommend.

Defense R&D has led to numerous breakthroughs in military systems, and many mainstream commercial technologies like the internet and self-driving cars can trace their roots back to Pentagon projects. Cutting S&T spending may have few short-term consequences, but “neglect of these earlier-stage research and development activities could … depriv[e] the U.S. defense sector of the critical underpinnings necessary for maintaining technological superiority and global dominance in the future,” the report said.

While S&T funding remains below recommended levels, spending rose in recent years in proportion to the total Defense Department budget. In fiscal 2011, the Pentagon only spent 1.7 percent of its total funds on S&T, and the proportion has steadily climbed every year since.

That said, S&T spending in absolute dollars has plateaued during the last decade. Early-stage R&D funding grew at a compound rate of 4.6 percent every fiscal year between 1978 and 2006, but only one-tenth of a percentage point in the years since. Spending peaked at $16.3 billion in fiscal 2005.

Last year, the Pentagon spent $2.2 billion—roughly 16.4 percent of the S&T budget—on basic research, which it defines as “farsighted high payoff research that provides the basis for technological progress.” The Coalition for National Security Research in 2015 suggested basic research account for one-fifth of S&T spending, or about $500 million more than was allocated in 2017.

But under the Trump administration’s 2019 budget proposal, the Pentagon would find much more in its R&D coffers.

Funding for research, development, testing and evaluation—a broad category that includes S&T—would grow by $13.5 billion, up 31 percent from the 2018 allocation. However, the proposal’s 19 percent cut to non-Defense spending would force virtually every other agency to drastically tighten its research purse strings.